Are we beginning to commend ourselves again? Or do we need, as some do, letters of recommendation to you, or from you?  You yourselves are our letter of recommendation, written on our hearts, to be known and read by all.  And you show that you are a letter from Christ delivered by us, written not with ink but with the Spirit of the living God, not on tablets of stone but on tablets of human hearts.
 Such is the confidence that we have through Christ toward God.  Not that we are sufficient in ourselves to claim anything as coming from us, but our sufficiency is from God,  who has made us competent to be ministers of a new covenant, not of the letter but of the Spirit. For the letter kills, but the Spirit gives life. (2 Cor 3:1–6)
Verse 6, the comparison between the letter and the Spirit, is often used to contrast the ineffectiveness of the Mosaic law against the power of the indwelling Spirit of Christ. And indeed, the context of the following verses in which the “ministry of death, carved in letters on stone,” clearly referring to the tablets given at Sinai as opposed to the ministry of the Spirit, suggests a comparison between the Decalogue and the Holy Spirit given to believers.
But the letter/Spirit antithesis actually goes further. It is not only the Decalogue – the law which is indeed “holy and righteous and good” (Rom 7:12) according to Paul – which is ineffective. It is any external code, any external effort whatsoever that does not rely upon the Spirit of God for transformation.
T. J. Deidun advances that proposition in his discussion of 2 Corinthians 3:
Now we may safely presuppose that Paul did not arrive at the conclusion that the γράμμα ‘kills’ by way of anthropological reflection on the effect that law has on man. It is the [C]hristian experience of the life-giving Spirit as eschatological newness that enables Paul to see that only the Spirit brings life and hence only the ‘new creation’ effected by the Spirit can bring man from death to life and from sin to [justification]. The primary datum of [C]hristian experience is not that the γράμμα ‘kills’ (that is a subsequent inference) but that the Spirit (and only the Spirit) [gives life].
It is important to note that neither Deidun, nor this author, are advocating for a morality that is devoid of any external imperatives. Those imperatives – grounded in the indicative of the believer’s position in Christ and as a temple for His Spirit – are indeed necessary on this side of glory while we remain imperfect. Indeed, Deidun remarks, “even in the [C]hristian economy external imperatives are to be seen chiefly as a sign of imperfect liberation. …”
As our series continues, we shall see how Paul uses imperatives, commands and exhortations in cooperation with the Spirit to encourage our growth in holiness.
But those imperatives are not the external code of a former covenant that failed to produce righteousness. It is that external code of death that produced sin in the flesh of the unregenerate Paul. It is that external code of death that was given to increase transgression until Christ came. It is that external code of death that the Judaizers wanted to impose upon the Galatians who had been running well and now were stumbling.
And it is that external code of death that is the antithesis of a life in the Spirit.